A fiber optic gyroscope with counter-propagating electromagnetic waves in a fiber optic coil senses rotation about the coil. Such a fiber optic gyroscope uses a bias modulation to bias the gyroscope on a rate sensitive portion of an interferogram and demodulation to measure and report rotation rates. A bias modulation synchronous with demodulation circuitry provides for the highest sampling efficiency and best gyroscope performance. A synchronous fiber optic gyroscope requires tunable system clocks that are greater than 30 MHz. Such clocks are typically created using commercial off-the-shelf direct digital synthesizers.
Radiation-hardened high performance fiber optic gyroscopes are needed for strategic applications in harsh environments such as outer space. Unfortunately, radiation hardened electrical components cannot operate as fast as commercial parts, therefore requiring radiation hardened fiber optic gyroscope modulation/demodulation circuitry to run asynchronously, resulting in lower performance.
In addition, radiation-hardened direct digital synthesizers are not currently available, and high-speed radiation-hardened digital-to-analog converters, which are needed to create a discrete direct digital synthesizer in the digital domain, are also not available. Therefore, a conventional radiation-hardened fiber optic gyroscope is typically asynchronous, where a low-speed discrete direct digital synthesizer is used to create a low-frequency modulation signal, which is asynchronous to the system clock used to sample the signal at an analog-to-digital converter.